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91.
J.?F.?Q.?Rey T.?S.?Plivelic R.?A.?Rocha S.?K.?Tadokoro I.?Torriani E.?N.?S.?MuccilloEmail author 《Journal of nanoparticle research》2005,7(2-3):203-208
This paper describes the synthesis of indium oxide by a modified sol–gel method, and the study of thermal decomposition of the metal complex in air. The characterization of the intermediate as well as the final compounds was carried out by thermogravimetry, differential thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and small angle X-ray scattering. The results show that the indium complex decomposes to In2O3 with the formation of an intermediate compound. Nanoparticles of cubic In2O3 with crystallite sizes in the nanosize range were formed after calcination at temperatures up to 900°C. Calcined materials are characterized by a polydisperse distribution of spherical particles with sharp and smooth surfaces.This revised version was published online in August 2005 with a corrected issue number. 相似文献
92.
P.?K.?Ghosh S.?Das K.?K.?ChattopadhyayEmail author 《Journal of nanoparticle research》2005,7(2-3):219-225
Nanocrystallites of cadmium oxide (CdO) thin films were deposited by sol–gel dip coating technique on glass and Si substrates. XRD and TEM diffraction patterns confirmed the nanocrystalline cubic CdO phase formation. TEM micrograph of the film revealed the manifestation of nano CdO phase with average particle size lying in the range 1.6–9.3 nm. UV–Vis spectrophotometric measurement showed high transparency (nearly 75% in the wavelength range 500–800 nm) of the film with a direct allowed bandgap lying in the range 2.86–3.69 eV. Particle size has also been calculated from the shift of bandgap with that of bulk value for the films for which the particles sizes are comparable to Bohr exitonic radius. The particle size increases with the increase in annealing temperature and also the intensity of XRD peaks increases which implies that better crystallinity takes place at higher temperature.This revised version was published online in August 2005 with a corrected issue number. 相似文献
93.
94.
ZENG Zhaoquan WANG Yong DU Xiaolong MEI Zengxia KONG Xianghe JIA Jinfeng XUE Qikun & ZHANG Ze . State Key Laboratory for Surface Physics Institute of Physics Chinese Academy of Sciences Beijing China . Laboratory of Electron Microscopy Institute of Physics Chinese Academy of Sciences Beijing China . College of Physics Engineering Qufu Normal University Qufu China . Beijing University of Technology Beijing China 《中国科学G辑(英文版)》2004,47(5):612-620
ZnO is a wide direct bandgap (Eg=3.37 eV at room temperature) II-VI compound semiconductor of wurtzite structure (a = 3.249 ? c = 5.207 ?. Compared to GaN and ZnS, ZnO has a larger exciton binding energy, ~60 meV (cf. ~25 meV for GaN and ~40 meV for ZnS), which is advantageous to realizing low-threshold excitonic lasers. Since optically pumped UV lasing of ZnO at room temperature was reported in 1997[1], much attention has been paid to the crystal quality improvement and p-type conduc… 相似文献
95.
在氮气、氢气以及氯化铵热解产生的氨气环境下,以钴作为催化剂,在780℃—940℃温度范围内使二甲苯与二茂铁受热分解,合成了CNx纳米管.在高分辨率透射电子显微镜下观察,合成的纳米管呈现“锥形嵌套”的形貌特征.从不同结构的分子面形成能的角度探讨了CNx纳米管的催化生长机理.不同温度下所制备样品的拉曼光谱研究表明,ID/IG值可以反映氮的掺杂所带来的纳米管结晶有序程度的降低,并通过G带向高波数移动证实了氮的掺杂. 相似文献
96.
The atomistic simulation results presented in Part I for SrTiO3 (310) symmetrical tilt grain boundary (STGB, the so-called = 5 GB with 36.8° symmetrical misorientation about [001]) are analyzed in the context of available experimental studies. In particular, atomic imaging studies of SrTiO3 GBs via high resolution TEM and incoherent Z-contrast STEM imaging; and determination of oxygen positions by combining electron energy loss spectroscopy (EELS) and bond-valence-sum rules, are compared with simulation results. The atomistic simulation data on the GB energies are compared with relative experimental estimates obtained via a novel approach of faceting of focused ion beam (FIB) induced microvoids.While there are considerable differences in details of simulation and experimental results, some basic trends seem to emerge about the core structural framework of GBs in SrTiO3. The paper highlights the limitations of both, experimental and simulation techniques, and argues in favor of synergistic use of diverse experimental and simulation approach to determine the atomic structure and properties of GBs. 相似文献
97.
对生长在Si和MgO单晶基片上的不同厚度的单层NbN薄膜、双层薄膜AlN/NbN以及三层薄膜NbN/AlN/NbN应用透射电子显微镜(Transmission Electron Microscope,TEM)技术进行了分析研究,对这几种薄膜样品的微观结构、薄膜厚度以及各个边界的一些直观细节给出了较为清晰的图像。由透射电子显微镜的电子衍射图案计算了薄膜和单晶衬底的晶格常数,并与我们以前采用X射线衍射技术分析的结果进行了比较,结果有很好的吻合。 相似文献
98.
Novel Broadband Reflectarray Antenna with Windmill-Shaped Elements for Millimeter-Wave Application 总被引:1,自引:0,他引:1
Hua Li Bing-Zhong Wang Ping Du 《International Journal of Infrared and Millimeter Waves》2007,28(5):339-344
A novel broadband millimeter-wave reflectarray antenna composed of windmill-shaped elements of variable lengths is proposed.
Compared to the conventional single-layer reflectarray elements, the windmill-shaped elements can realize much larger phase
variation range (over 600°), leading to broader bandwidth. Using this technique, a 15°-beam-steering reflectarray operating
at 30 GHz is designed. The computed results demonstrate the agreement of the main beam steering with the design requirement,
and a 1-dB gain bandwidth close to 20% is obtained. The validity of the obtained results is verified by comparing the ones
generated by Ansoft High Frequency Structure Simulator (HFSS) with those produced by Ansoft Designer. The antenna is useful
for millimeter-wave applications.
This work was supported by the National Natural Science Foundation of China (No. 90505001), the High-Tech Research and Development
Program of China (No. 2006AA01Z275), and the Creative Research Group Program of UESTC. 相似文献
99.
Q. Md. Alfred T. Chakravarty G. Singh S. K. Sanyal 《International Journal of Infrared and Millimeter Waves》2007,28(10):881-887
In radar, planar phased array antenna plays vital role in electronic scanning in the azimuth and elevation direction to the
horizon. In most operations using planar phased array both the coordinates of azimuth and elevation, are steered electronically.
In this paper a conceptual schematic of a phased array antenna with programmable time delay units has been presented. It is
shown that by suitably exploiting the time delay matrix one can have electronic beam rotation around the target axis as required
in conical scan. Thus both the elevation and azimuth motors in conical scan system are replaced by electronic scanning. Heuristically,
we have selected eight consecutive points for beam rotation in a polygon shape and can also be extended almost circular shape
by increasing number of array elements and phase shifter (delays) in the delay matrix. The array requires dual control of
phase gradient and individual phase values. The whole array is controlled by micro-controller. This presents exciting possibilities
in radar operation. 相似文献
100.
The formation of Ag nanoparticles synthesized by homogeneous nucleation, stabilized by polymers (PVA and PVP) was monitored
by UV–Vis spectrophotometry and transmission electron microscopy. Our aim was to differentiate between the two main phases
of particle formation, i.e. nucleation and growth and to characterize their rates with the help of appropriate kinetic equations.
Time resolved spectrophotometric measurements revealed that particle formation is an autocatalytic process: a slow, continuous
nucleation phase (3–5 min) is followed by a rapid, autocatalytic growth phase where the maximal particle size is 5–7 nm. By
freezing the reaction mixture, the process of particle growth can be followed from 5 to 40 min on TEM pictures. The first
order rate constants were calculated and they are strongly depend on the polymer concentration. If the growing particles are
attached by PEI to the surface of a solid support, the formation of silver nanoparticles can also be followed by atomic force
microscopy (AFM) and we can control the particle growth on mica surface. The cross section analysis of the pictures show,
that the particle growing process can be also monitored at solid–liquid interface. 相似文献